fix #69: missing first word in sse response for example_app

[wliu6v]

The example app will retrieve the corresponding item with the message.id from the list after each response is returned, and append the returned content to it. However, the first response is discarded (because the message object is null, so the message?.message = .... does not function properly).

After merging PR #80, due to the SSE fix, the first response that sets the role (where message is empty) can now correctly return to the example app. Therefore, even if the example app discards the message from the first return, there is no significant impact. However, this is not reasonable, so a fix is needed for this issue.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (58ec1dc) 83.87% compared to head (dff7076) 83.87%.

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Additional details and impacted files

@@           Coverage Diff           @@
##             main      #81   +/-   ##
=======================================
  Coverage   83.87%   83.87%           
=======================================
  Files          71       71           
  Lines        1048     1048           
=======================================
  Hits          879      879           
  Misses        169      169           

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